Patent GB-811209-A (GB)
Title: Butene dehydrogenation
IPC: C07C5/333
Filed: 1957-09-13
Abstract: In a butene dehydrogenation process wherein superheated steam and butene are contacted with a dehydrogenation catalyst and wherein the catalyst is regenerated by burning with steam and excess air, steam and air effluent from a regenerator is burnt with a fuel to remove <PICT:0811209/III/1> the oxygen and the oxygen-free steam is recirculated to a dehydrogenation reactor as a portion of the steam requirement thereof.  The catalysts in the dehydrogenation and regeneration process may be calcium nickel phosphate, magnesia iron oxide, magnesia chromia or zinc oxide-iron oxide with or without a potassium promoter.  The supply of fresh steam, recycled steam and butene to the reactor, and steam and air to the regenerator may be reversed so that the chambers containing respectively the active dehydrogenation catalyst and deactivated dehydrogenation catalyst can become the regenerator and reactor dependent upon the state of the catalysts.  In the Figure shown, when A is the reactor and B the regenerator, preheated butene from line 1, furnace 3, valve 4 and line 5 meets superheated steam from coils 10, furnace 11, line 12, valve 13 and line 14 at line 6 and passes to line 7 where it is also joined by recycled steam from the regenerator B and the gaseous mixture enters the reactor A containing the active catalyst. Butadiene is formed in the reactor A, at this stage, at temperatures between 1000-1300 DEG  F. and is recovered from line 9 as a crude product.  The regenerator, vessel B, is supplied with steam and air respectively from the furnace 11 by line 12, valve 13 to line 16, and line 17 and the steam-air mixture passes into the regenerator B containing deactivated catalyst.  There is no flow, at this stage, through lines 19 and 20.  The steam-air effluent leaves the regenerator B by line 21 and passes to a burner 22 where it is burnt with a fuel from line 23 to remove the oxygen present in the air and the products, for example, CO2, CO, N2 and H2O are recycled to the reactor A by lines 25 and 7.  To change the reactor A into the regenerator A, and vice versa, for example, after 10-60 minutes, steam only is passed for a short while to purge the regenerator-reactor vessels of residual gases and the air supply to the burner 22 is maintained by opening valve 31 of air inlet line 30, 32. Preheated butene then flows through valve 4 and line 20 to meet fresh steam from furnace 11 via line 16 and recycled steam from burner 22 by line 19 and the mixture passes into the reactor B with a crude butadiene recovery line 27.  Valve 26 is closed and there is no flow through lines 21.  Similarly, the regenerator is fed with steam from lines 12, 14, 6 and 7, and air from air inlet line 28 and opened valve 15.  The steam-air effluent from the regenerator A passes through valve 8, line 29 into burner 22 with fuel injection line 23, as before, and the oxygen-free steam passes to the reactor B via line 19.  Any carbonaceous fuel may be used to remove the oxygen from the steam-air effluent of the regenerator and may be gaseous, solid or liquid and, is preferably in 20-25 per cent excess of the air.  An oxidation or reforming catalyst may also be present to ensure complete oxygen removal.ALSO:<PICT:0811209/IV (b)/1> In a butene dehydrogenation process to form butadiene wherein superheated steam and butene are contacted with a dehydrogenation catalyst and wherein the catalyst is regenerated by burning with steam and excess air, steam and air effluent from a regenerator is burnt with a fuel to remove the oxygen and the oxygen-free steam is recirculated to a dehydrogenation reactor as a portion of the steam requirement thereof.  The flow of gases may be redirected so that the dehydrogenation reaction chamber becomes the regenerator when the catalyst is deactivated and the regenerator becomes the dehydrogenation reaction chamber when its catalytic contents are active.  In the Figure shown, when A is the reactor and B the regenerator, preheated butene from line 1, furnace 3, valve 4 and line 5 meets superheated steam from coils 10, furnace 11, line 12, valve 13 and line 14 at line 6 and passes to line 7 where it is also joined by recycled steam from the regenerator B and the gaseous mixture then enters the reactor A containing active catalyst. Butadiene is formed in the reactor at a temperature between 1000-1300 DEG  F. and is recovered as a crude product from line 9.  At the same time, steam from line 12 is led through valve 13 to line 16 where it is admixed with air from line 17 and the mixture passes to the regenerator B containing the catalyst in a deactivated state.  There is no flow, at this stage, through lines 19 and 20.  The deactivated catalyst is reoxidized to its normal state of oxidation and any carbonaceous deposits are removed. The steam-air effluent leaves the regenerator B by line 21 and passes to a burner 22 where it is burnt with fuel from a line 23 to remove the oxygen present in the air. The oxygen-free steam and the products of combustion of air, for example CO2, CO and N2, are then passed to the reactor A through lines 25 and 7.  To change the reactor A to the regenerator A, or vice versa, for example, after 10 to 60 minutes, steam only is passed for a short while through the regenerator to remove residual gases and the air supply to the burner 22 is maintained by the entry of air from air line 30, 32 with valve 31 open.  Pre-heated butene then flows through valve 4 and line 20 to meet fresh steam from line 16 and recirculated steam from the burner 22 by line 19 and the mixture passes into the reactor B and the crude butadiene product is recovered from line 27, via a valve 26, there being no flow in line 21.  The regenerator A is simultaneously fed with steam from lines 12, 14, 6 and 7 and air through an opened valve 15 and line 28.  The steam-air effluent from the regenerator A passes through a valve 8 to line 29 and into the burner 22 where fuel is injected from line 23 as before and the oxygen-free steam is recycled to the reactor B by line 19.  The catalysts in the dehydrogenation process may be calcium nickel phosphate, magnesia iron oxide, magnesia chromia or zinc oxide-iron oxide with or without a potassium promoter.  Any carbonaceous fuel may be used to remove the free oxygen in the steam-air effluent of the regenerator, and may be gaseous, solid or liquid and is preferably in 20-25 per cent in excess of the air.  An oxidation or reforming catalyst may also be present to ensure the complete removal of oxygen.